Chemoenzymatic Labeling to Visualize Intercellular Contacts Using Lipidated SortaseA

Methods to label intercellular contact have attracted attention because of their potential in cell biological and medical applications for the analysis of intercellular communications. In this study, a simple and versatile method for chemoenzymatic labeling of intercellularly contacting cells is demonstrated using a cell‐surface anchoring reagent of a poly(ethylene glycol)(PEG)‐lipid conjugate. The surface of each cell in the cell pairs of interest were decorated with sortase A (SrtA) and triglycine peptide that were lipidated with PEG‐lipid. In the mixture of the two‐cell populations, the triglycine‐modified cells were enzymatically labeled with a fluorescent labeling reagent when in contact with SrtA‐modified cells on a substrate. The selective labeling of the contacting cells was confirmed by confocal microscopy. The method is a promising tool for selective visualization of intercellularly contacting cells in cell mixtures for cell‐cell communication analysis. A simple and versatile strategy toward selective fluorescent labeling of intercellular contacting cells is reported. A transpeptidase sortase A and its substrate triglycine peptide were conjugated with a lipidated polymer, leading to anchoring onto cell membranes. The triglycine‐modified cells were labeled with a fluorescent dye by contacting with the sortase A‐modified cells based on proximity‐dependent transpeptidation.